1 A Distributed Architecture for Multimedia in Dynamic Wireless Networks By UCLA C.R. Lin and M. Gerla IEEE GLOBECOM'95.

2 Outline Introduction Definitions The Multicluster Architecture and its Properties Adaptive Routing for Real-Time Traffic Conclusion Discussion

3 Introduction To support multimedia services (voice, data, video, and image) Real-time traffic (voice, video)  delay-sensitive Bursty traffic (data, image)  error-sensitive

4 Definition Definition 1: (System Topology) Is a graph G=(V,E)  V is the set of nodes  E is the set of edges One transceiver (half-duplex) in each node Definition 2: (Distance of Two Nodes) Distance d (x,y )

5 Definition(cont.) Definition 3: (Cluster) C i V is a set of nodes C i : A cluster V = and C i ∩ C j =, if i ≠ j x, y C i, d (x,y )≤ 2 Definition 4: (Center and Radius of a Cluster) How to choose center(x o ) in C i d (x,y), x,y C i  d (x 0,y) is called the radius of a cluster

6 Definition (cont.) Definition 5: (Degree of Topology) Is the number of clusters in a topology ( ) Definition 6: Repeater Bridge u=(x,y) The Order of a Repeater

7 Definition 7: (Bridge Partially in a Cluster) 1

8 The Multicluster Architecture and its Properties (cont.) Centralized Clustering Algorithm: 0. i = 0 1. x = min(V ) 2. C i = {x } ∪ Γ 1 (x ) V = V – C i E = E – ω (C i ) 3. If V ≠ then i = i + 1 and goto 1; else stop Γ 1 (x ) be the set of one-hop neighbors of x C0C0 x

9 The Multicluster Architecture and its Properties (cont.) Robust Cluster structure Because can Re-cluster approach  d (1,4)=d (0,4)= 3>2  Find a highest degree node and its neighbors to stay in the original cluster to as a center, and remove the other nodes  The other nodes should either join another cluster or form a new cluster

10 Adaptive Routing for Real-Time Traffic Objective Real-time traffic can to transmit over the dynamic network, and the routing protocol is keep communication The routing optimality is of secondary importance Choose a hierarchical routing protocol

11 The Two-level Hierarchical Routing Protocol Route construction and Route maintenance The construction phase establishes an initial set of routes The maintenance phase maintains loop-free routing in the face of arbitrary topological changes

12 The Two-level Hierarchical Routing Protocol(cont.) Construction Phase Assume every node has no global connectivity information, but keeps some information of its locality  Locality information destination Cluster 0 Cluster 1

13 Construction Phase IFDB (internal forward database) Every node has to maintain for each repeater in its cluster a list of nodes to which the repeater has one or more routes EFDB (external forward database) every repeater has to maintain for each adjacent cluster a list of nodes to which the cluster has routes

14 Construction Phase(cont.) IFDB of node 1 may be ((4, {8, 15}) (3, {8, 16})), destination is node 15 EFDB of node 6 may be ((C 2, {1, 18}) (C 3, {1, 4}) (C 5, {17})) destination is node 4

15 Input repeaterOutput repeater repeater destination output repeater destination input repeater IFDB EFDB Case 1 Case 2

16 Construction Phase(cont.) If IFDB and EFDB do not include the destination Discovery packet Update IFDB Reply packet destination source

17 Construction Phase(cont.) The cluster-level topology be described to a graph A vertex represents a cluster and a link between two vertices Routes are built depending on the order of the reply packet transmission the cluster-level topology would be an acyclic directed graph (ADG)

18 Maintenance Phase Destination node The ID is DID x deletes DID from EFDB  (C j, {DID,... }) x y z z deletes DID from IFDB  (x, {DID,... }) CiCi CjCj Update packet

19 Maintenance Phase(cont.) Ex:

20 Re-clustering and how to establish a new route

21 Simulation range : N nodes randomly in 100x100 area Fig.3 Transmission range  connectivity

22 Fig.4 transmission range  cluster number (the degree of a topology) (the average number of nodes in a cluster) Simulation

23 Simulation Fig.6 The order of most repeaters is either 2 or 3 Fig.7 That more than 50% of nodes are repeaters over the interval(30, 80)

24 Simulation

25 Simulation Direction: U(0, 2π), distance: U(0, 3) Fig.10 The average number of nodes which switch clusters per 100ms is relatively small

26 Conclusion Provide a distributed multicluster architecture for transporting real-time traffic in a multihop dynamic radio networks A hierarchical routing protocol over the architecture is stable and loop-free in the face of topological change

27 Discussion Re-cluster problem

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29 The Multicluster Architecture and its Properties Clusterhead  May become bottleneck Fully distributed algorithm The system topology G(V, E ) is divided into small partitions (clusters ) with independent control Advantage: Permits us to avoid vulnerable centers and hot spots of packet traffic flow.

30 A hierarchical routing protocol’s main reasons Attempts to reduce traffic by hiding information about the content of a cluster Hierarchical structure can scale to large populations The multicluster infrastructure is quite stable in the mobile environment(Fig.10) and multiple links connect two adjacent clusters(Fig.8)

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